/**
 * Copyright (C) 2011 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.inject.internal;

import static com.google.common.base.Preconditions.checkNotNull;

import com.google.inject.internal.ProvisionListenerStackCallback.ProvisionCallback;
import com.google.inject.spi.Dependency;

import javax.inject.Provider;

/**
 * Base class for InternalFactories that are used by Providers, to handle
 * circular dependencies.
 *
 * @author sameb@google.com (Sam Berlin)
 */
abstract class ProviderInternalFactory<T> implements InternalFactory<T> {

    protected final Object source;

    ProviderInternalFactory(Object source) {
        this.source = checkNotNull(source, "source");
    }

    protected T circularGet(final Provider<? extends T> provider, final Errors errors, InternalContext context, final Dependency<?> dependency, ProvisionListenerStackCallback<T> provisionCallback) throws ErrorsException {
        final ConstructionContext<T> constructionContext = context.getConstructionContext(this);

        // We have a circular reference between constructors. Return a proxy.
        if (constructionContext.isConstructing()) {
            Class<?> expectedType = dependency.getKey().getTypeLiteral().getRawType();
            // TODO: if we can't proxy this object, can we proxy the other object?
            @SuppressWarnings("unchecked")
            T proxyType = (T) constructionContext.createProxy(errors, context.getInjectorOptions(), expectedType);
            return proxyType;
        }

        // Optimization: Don't go through the callback stack if no one's listening.
        constructionContext.startConstruction();
        try {
            if (!provisionCallback.hasListeners()) {
                return provision(provider, errors, dependency, constructionContext);
            } else {
                return provisionCallback.provision(errors, context, new ProvisionCallback<T>() {
                    public T call() throws ErrorsException {
                        return provision(provider, errors, dependency, constructionContext);
                    }
                });
            }
        } finally {
            constructionContext.removeCurrentReference();
            constructionContext.finishConstruction();
        }
    }

    /**
     * Provisions a new instance. Subclasses should override this to catch
     * exceptions & rethrow as ErrorsExceptions.
     */
    protected T provision(Provider<? extends T> provider, Errors errors, Dependency<?> dependency, ConstructionContext<T> constructionContext) throws ErrorsException {
        T t = errors.checkForNull(provider.get(), source, dependency);
        constructionContext.setProxyDelegates(t);
        return t;
    }
}
